Shredding machine, and method of providing a time delay in a shredding machine

ABSTRACT

A shredding machine comprises a housing, a shredding mechanism, a motor for operation of the shredding mechanism, a slot through which documentary material is fed for shredding by the mechanism, and an operating member movable from an operative position in which it extends across the slot, to an inoperative position retracted from the slot, in consequence of the feeding of the material into the slot, and returning, in the absence of the material in the slot, to its operative position under the action of a spring. A motor controller includes a microswitch having a plunger which is spring-urged into a projecting position, in which it is open circuit. The spring urges the operating member into its operative position. Thus, when material enters the slot, moving the operating member to its inoperative position, the plunger is depressed to start or permit operation of the shredding mechanism. A damper is interposed between the operating member and the resilient device, and includes a shallow cylindrical chamber within which a cylindrical drive member is mounted for rotary movement, such a movement being retarded by viscous material within the chamber. The drive member is connected to a drive arm, one end of which engages the operating member, the other end of which engages the plunger of the microswitch. Thus, on completion of passage of the material through the slot, releasing the operating member for movement to its operative position, the movement of the operating member to its operative position is retarded, allowing completion of passage of the sheet.

DESCRIPTION OF INVENTION

This invention is concerned with improvements in shredding machines.

A conventional shredding machine (hereinafter referred to as being ofthe kind specified) comprises a housing in which a shredding mechanismis mounted, drive means being provided for the shredding mechanism.Mounted over the housing is a cover provided with a slot through whichmaterial to be shredded is fed, into engagement with shredding mechanismof the machine.

Desirably sensing means is provided in the machine, to terminateoperation of the drive means when the machine is not being used, or whenuse has been completed. A convenient sensing means which mayconveniently be incorporated into the machine comprises an opticalsensor, responsive to the presence of a sheet of paper in the slot toactivate, or permit activation of the drive means, and to terminateoperation of the drive means when the paper has passed through the slot.

Such sensing means are expensive, and an alternative sensing means maybe provided by a microswitch having an operating member which isspring-urged into an operative position in which it extends across themouth. The operating member is thus engaged by the paper as it isinserted into the slot, to cause the microswitch to close and to causeoperation of the shredding mechanism to commerce.

However, a further problem with shredding machines of the kind specifiedis that, to allow complete passage of material through the slot andthrough the shredding mechanism, it is necessary to utilise a time delayto maintain operation of the shredding mechanism for a short period oftime subsequent to completion of passage of the material beyond theoperating member. Conventionally such a time delay is afforded by anelectronic mechanism, which adds to the cost of the machine.

According to this invention there is provided a shredding machinecomprising:

a) a housing;

b) shredding mechanism in the housing;

c) a slot in the housing, through which material to be shredded entersthe housing; and

d) and operating member urged by resilient means into an operativeposition in which it extends across the mouth of the slot, to be movedto an inoperative position by entry of the material to be shredded intothe housing, to cause the shredding mechanism to operate;

characterised in that there is interposed between the resilient meansand the operating member a motion damping device.

Conveniently, the resilient means is provided by spring means by whichthe plunger of a microswitch is urged to its open condition. Thusmovement of the operating member to its inoperative position causesmovement of the damping device against the plunger of the microswitch,causing the microswitch to adopt its closed condition, to cause theshredding mechanism to operate. On passage of the material beyond themouth, the operating member is released, and the damping device retardsmovement of the resilient means, delaying switching of the microswitchfor a short period of time sufficient to allow completion of passage ofmaterial into the shredding mechanism.

According to this invention there is also provided a shredding machinecomprising

a) a housing;

b) shredding mechanism in the housing;

c) a drive motor in the housing to drive the shredding mechanism;

d) control means in the housing for the drive motor, said control meanscomprising a microswitch having a plunger spring-urged into acircuit-open condition;

e) a slot in the housing through which material to be shredded may enterthe housing; and

f) an operating member mounted adjacent the slot for movement between anoperative position in which it extends across the mouth of the slot, andan inoperative position, movement of the operating member to itsinoperative position being caused by entry of material to be shreddedinto the slot, the microswitch providing resilient means whereby theoperating member is urged into its operative position,

characterised in that there is interposed between the operating memberand the resilient means a motion damping device whereby movement of theoperating member under the action of the resilient means to itsoperative position is retarded.

Conveniently the damping device is a rotary damping device comprising ashallow cylindrical housing, and a drive member mounted in the housingwith a small clearance between the interior wall of the housing and theexterior wall of the drive member, there being a viscous material, suchas a viscous oil or elastomeric material, in said space to retard rotarymovement of the drive member within the housing. Preferably attached tothe drive member is a drive arm, extending generally diametrically ofthe device, one end of which engages the operating member, the other endof which engages the plunger of the microswitch.

Preferably said operating arm is L-shaped, and conveniently theoperating member is freely mounted for movement relative to the housingof the machine.

According to this invention there is also provided a method of providinga time delay in a shredding machine to maintain operation of theshredding mechanism for a short period of time subsequent to completionof passage of the material through an entry slot of the machine, inwhich the delay is afforded by the use of a motion damping device.

There will now be given a detailed description, to be read withreference to the accompanying drawings, of a shredding mechanism whichis a preferred embodiment of this invention, having been selected forthe purposes of illustrating the invention by way of example.

In the accompanying drawings:

FIG. 1 is a sectional view of part of a cover of the preferredembodiment, showing the material entry slot thereof;

FIG. 2 is a side elevation on FIG. 1, showing an operating memberprojecting across the entry slot in an operative position,

FIG. 3 is a view showing the plunger in an inoperative position;

FIG. 4 is a sectional view through a damping device of the machine; and

FIG. 5 is a sectional view of a modified form of the preferredembodiment.

The shredding machine which is the preferred embodiment of thisinvention is a machine of the kind specified, comprising a housing 4within which is mounted shredding mechanism 5. Mounted in the housing 4is a drive motor 6, and a motor controller 7. The housing comprises acover 8 within which there is provided a material entry slot 10, throughwhich material to be shredded may be fed into the housing, to beshredded by the shredding mechanism.

Secured to the interior of the cover adjacent to the slot is a supportbracket 12, which carries an operating member 14, mounted for movementtherein between an operative position, in which a nose portion 15extends across the slot (shown in FIGS. 1 and 2) and an inoperativeposition in which it does not. Resilient means is provided, as will bedescribed hereinafter, to urge the operating member into its operativeposition.

The machine comprises a microswitch 20 comprising a plunger 22 which isspring urged into a projecting position (shown in FIG. 2), in which itis open circuit, and in which the shredding mechanism does not operate.

Also mounted on the underside of the cover 8 is a rotary damping device26, comprising a cylindrical housing 28 providing a damping chamber 38,closed by a cover 39, within which chamber drive member 29 is mountedfor rotary movement. Within the space between the exterior surfaces ofthe drive member 29 and the interior surfaces of the housing 28, aviscous fluid is provided, conveniently a viscous oil or a gel, toretard movement of the drive member 29 in the cylinder 28. The drivemember is secured by an axial shaft 37, passing through the cover 39, toa drive arm 30, in the preferred embodiment of L-shape, one end portion30 a of which is located adjacent to the plunger 22 of the microswitch,the opposite end portion 30 b of which is in engagement with theoperating member 14.

At rest, the spring means of the microswitch urges the plunger into itsprojecting position, causing the operating arm 30 to act on theoperating member 14 to cause it to adopt its operative position, inwhich it projects across the slot 10.

When a sheet 3 of documentary material is entered into the slot, as isshown in FIG. 1, the material presses the nose portion 15 of theoperating member 14 rearwardly, causing the drive arm 30 to rotate in aclockwise direction from the position shown in FIG. 2 to the positionshown in FIG. 3, depressing the plunger 22 of the microswitch, closingan electric circuit and causing the shredding mechanism to operate, todraw the sheet material through the slot. On completion of passage ofthe sheet through the slot, the operating member 14 is again allowed tomove from its inoperative position shown in FIG. 3 to its operativeposition shown in FIG. 2, under the force of the resilient means of themicroswitch. However the rotary damping device retards movement of theplunger 22, and a short delay occurs before the microswitch adopts itsoff condition, causing operation of the shredding mechanism to bemaintained for a short period of time—typically 1-2 seconds, afterpassage of the sheet beyond the nose 15. Such movement it will beappreciated simultaneously causes the nose portion 15 of the operatingmember 14 to move into the slot.

In the modified form of the preferred embodiment shown in FIG. 5, inwhich similar numerals increased by 100 have been utilised to indicateparts similar in construction and operation to those of the preferredembodiment, the rotary damping device 126 is offset from the axis ofrotation of the drive arm 130. The cylindrical drive member 129 isprovided at its axis of rotation with a ring gear 88, engageable withgearing 98 provided on the drive arm 130, and extending partly aroundthe axis of rotation of the drive arm 130.

In this way, a small movement of the drive arm, as produced in theoperation of the machine, produces an increased rotation of the drivemember 129, and thus increases the sensitivity of the arrangement.

It will be appreciated that the period of delay will be relativelyshort, and may to some extent be determined by the geometry of thearrangement, in particular the distance between the plunger 22 of themicroswitch and the longitudinal axis of the damping device, whereby themechanical advantage may be changed. Alternatively or in addition, theperiod may be varied by changing the viscosity of the viscous materialin the damping chamber.

In the present specification “comprise” means “includes or consists of”and “comprising” means “including or consisting of”.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately, or in any combination of such features, be utilised forrealising the invention in diverse forms thereof.

What is claimed is:
 1. A shredding machine, comprising: a) a housing; b)a shredding mechanism in the housing; c) a slot in the housing throughwhich a material to be shredded enters the housing; d) an operatingmember urged by a resilient means into an operative position in whichthe operating member extends across a mouth of the slot, to be moved toan inoperative position by entry of the material to be shredded into thehousing, to cause the shredding mechanism to operate; and e) a motiondamping device interposed between the resilient means and the operatingmember.
 2. The shredding machine according to claim 1, wherein theresilient means comprises a spring means by which a plunger of amicroswitch is urged to an open condition.
 3. The shredding machineaccording to claim 1, wherein the motion damping device includes a drivemember and a viscous material for retarding movement of the drivemember.
 4. The shredding machine according to claim 3, wherein theoperating member is operative to move the drive member in a cylindricalchamber.
 5. The shredding machine according to claim 4, wherein thecylindrical chamber is shallow, and wherein the drive member is mountedin the cylindrical chamber with a small clearance between an interiorwall of the cylindrical chamber and an exterior wall of the drivemember, and wherein the viscous material is provided in said clearance.6. The shredding machine according to claim 3, wherein the motiondamping device includes a drive arm connected to the drive member, thedrive member having one end which engages the operating member, andanother end which engages a plunger of a microswitch.
 7. The shreddingmachine according to claim 6, wherein the drive arm is L-shaped.
 8. Theshredding machine according to claim 1, wherein the motion dampingdevice includes a cylindrical chamber, a drive member mounted for rotarymovement in the chamber, and frictional resistance means in the chamberfor retarding the movement of the drive member, said drive membercarrying a drive arm having one end which engages the operatingmember,and another end which engages a plunger of a microswitch.
 9. Ashredding machine, comprising: a) a housing; b) a shredding mechanism inthe housing; c) a drive motor in the housing for driving the shreddingmechanism; d) a control means in the housing for the drive motor, saidcontrol means including a microswitch having a plunger spring-urged intoa circuit-open condition; e) a slot in the housing through which amaterial to be shredded enters the housing; f) an operating membermounted adjacent the slot for movement between an operative position inwhich the operating member extends across a mouth of the slot, and aninoperative position, the movement of the operating member to itsinoperative position being caused by entry of the material to beshredded into the slot, the microswitch providing a resilient means forurging the operating member into said operative position; and g) amotion damping device interposed between the operating member and theresilient means, for retarding the movement of the operating memberunder the action of the resilient means to said operative position.